The overall objective of the proposed research project is to use neurophysiological measures to assess and investigate bilingualism and to compare bilinguals' performance with that of monolinguals. Event-related potentials (ERPs) will be recorded and identified during the subjects' processing of sentences. Attention will center on the effects of contextual factors in language processing and, in particular, on the processing of target items that are embedded in sentence frames. Variables of interest will be the language proficiency of the subjects (Experiment 1) ad processing strategy (Experiment 2). In addition, the relationship between the target and the sentence frame will vary in terms of semantic incongruity (Experiments 1-4), language (Experiment 3), and stimulus modality (Experiment 4). Previous research by the investigator has identified two interesting phenomena: (a) a diminished N400 in Spanish-English bilingual subjects when they are processing Spanish sentences; and (b) a lateralized P600 response found more prominently when the sentences are presented auditorially. The present studies will explore various explanations or these effects. In addition, the studies will be related to theoretical issues in the assessment of bilingualism, language representation, and the strategic control over language processes. Inasmuch as little is known about the neurophysiological correlates of bilingualism, it is anticipated that these experiments on individuals with an intact system of language processing may provide basic information that will be useful in the assessment and remediation of language problems and in understanding language losses and recovery patterns in aphasia.